What technical blog should I write?

I have been writing a blog for almost a year. I have reflected on what I wrote in this year. Based on my situation, I have summarized what I should write in the following blog:

1. Problems Encountered during development, solutions, and causes of problems;

2. Better implementation used in development;

3. Answers and opinions of an algorithm or question;

4. learning experience;

So what should I not write?

For me, I think that simple Excerpt from books should not be written into a blog. It will not improve myself, nor help others. It is a thankless task.

Leave a note as a reminder to you.